Earthquake swarms


Apr 29, 2014
What the director has to say is certainly historically correct in some instances, but isn't particularly useful or pragmatic as it relates to short/long term predictions going forward. The simple fact remains, that even in the presence of numerous smaller quakes (think Yellowstone awhile back, or recently NNE of Punta Cana), making any sort of prediction as to future events is the equivalent of a coin toss.

The theory that earthquake swarms are a precursor to a much larger earthquake is based on the historical record of large earthquakes that have taken place in Japan, Iran, Italy and southeast Asia that followed a series of three or more smaller quakes in the same relative area or at least along the same fault within a distance of 150 miles or so.

I personally think that lots of smaller quakes tend to reduce the likelihood of a large centralized earthquake by releasing built up tectonic stress in a given area or at least equalizing those forces over a larger portion of the fault line. It appears from the historical record that swarms more often did not lead to a major seismic event than instances where they did. Obviously there may be some factors that we do not yet understand about earthquake swarms and a greater understanding may someday give the us the ability to use the occurrence of these swarms in a more useful and accurate way.

None-the-less, if one is into flipping a coin, which much of earthquake science is still equivalent to, then it is certainly understandable that for those whose job it is to predict these events and for those who live in vulnerable areas, it may not be a good idea to completely dismiss the possibility of a much larger quake occurring in these areas of sustained activity. I may not immediately head for safe ground, but at least for a few weeks I might be more prepared to do so than I otherwise might be.

We are currently much better at predicting volcanic eruptions than we are the forceful splitting of the earth's crust.

Ramón Delanoy, director of the center, explained that "when many small events are happening in an area, sometimes a great event occurs, but this does not mean that one will necessarily happen".


Happy to still be here
Oct 30, 2018
Interesting post, and one I might tend to agree with. Swarms of small (3.0 or less) earthquakes will relieve pressure when dispersed over a relatively large area. Say 100 Km. or so and could be resultant from larger ones such as the ones in Mexico and Chili (6.0 and 6.6 )
When located in or rather confined to one specific ridge or area, as the eruption in Hawaii if will certainly pose a threat.
Still a coin toss as to when though.


Welcome To Wonderland
Apr 1, 2014
Felt it here in Santiago. Friend felt it in Moca too. According to the
clock on my computer, lasted about 27 seconds.


May 3, 2000
USGS says measured 5.1 and epicenter was 24km SSE of Boca de Yuma, so it was felt just as strongly in Punta Cana.


Pro-Bono Demolition Hobbyist
Jul 24, 2004
5.8 135km SE of Punta Cana.

This one lasted a longer time, not jolts, but smooth movements for several seconds. The chandeliers were rocking.